This invention relates to sewing machines and, more particularly, to sewing machine work feeding mechanisms controllable in response to the successive application thereto of digital signals.
In recent years, so called "electronic" sewing machines have gained in popularity and have met with commercial success in both industrial and domestic applications. These electronic sewing machines typically include a memory unit for storing in digital form information to control both the needle positioning mechanism and the work feeding mechanism to automatically produce a desired pattern. Signals generated from the stored information are applied to signal responsive actuators for selectively positioning the needle and the work feeding mechanism. These actuators may be of either the analog type or the digital type. An analog actuator is responsive to an analog signal for positioning its associated mechanism at a point along a continuum between two extreme positions. The present invention is concerned with digital actuators wherein the actuator responds to digital input signals to position its associated mechanism at a selected one of a plurality of incrementally displaced discrete points between two extreme positions. A problem encountered with actuators of the digital type is that it is often desired to position the associated mechanism at a point intermediate two of the predetermined discrete positions.
It is therefore an object of this invention to provide a manually operable continuously movable override for a digital actuator.
A further problem inherent in the use of digital actuators becomes apparent when such an actuator is used in conjunction with a work feeding mechanism for a sewing machine. The feeding characteristics of different fabrics differ widely so that feed settings which result in equal stitch lengths in forward and reverse directions for one particular fabric, will not necessarily result in equal length stitch formation in forward and reverse directions when another fabric is sewn upon. The machine therefore has to be "balanced" for the particular fabric being stitched. When utilizing an actuator of the digital type, the balance point may lie between two of the predetermined incrementally displaced discrete positions.
It is therefore another object of this invention to provide a manually operable balance control for a sewing machine utilizing a digital actuator for the work feeding mechanism.